This invention relates generally to clamping devices and particularly to a powered clamp having a toggle action and to a gauging apparatus having a locking feature.
Powered clamps are commonly used in industrial applications for holding work pieces of many sizes and shapes during forming and machining operations. Such devices typically include a pneumatically or hydraulically actuated cylinder which causes one or more arms to move through a desired range of rotational motion to push against a work piece. Depending on the specific application, the user may wish to actuate one or two arms which may be vertically or horizontally aligned in an environment contaminated with weld splatter, saw chips, coolants, dust and dirt. One such conventional powered clamp is disclosed in U.S. Pat. No. 5,171,001 entitled "Sealed Power Clamp" which issued to the present inventor on Dec. 15, 1992 and is hereby incorporated herein by reference.
Other traditional powered clamps are disclosed in the following U.S. Pat. Nos. 4,905,973 entitled "Power Operated Clamp With Externally Mounted Adjustable Clamp Arm" which issued to Blatt on Mar. 6, 1990; 4,637,597 entitled "Locking Power Clamp" which issued to McPherson, et al, on Jan. 20, 1987; 4,496,138 entitled "Power Operated Clamp" which issued to Blaft on Jan. 29, 1985; 4,494,739 entitled "Power Operated Rotatable Clamping Assembly" which issued to Valentine on Jan. 22,1985; 4,458,889 entitled "Locking Power Clamp" which issued to McPherson, et al, on Jul. 10, 1984; 4,021,027 entitled "Power Wedge Clamp with Guided Arm" which issued to Blatt on May 3,1977; 3,702,185 entitled "Cylinder Operated Power Clamp" which issued to Blatt on Nov. 7, 1972; and 3,570,835 entitled "Power Operated Clamping Device" which issued to McPherson on Mar. 16, 1971. A limitation of these traditional clamps is that the arms will typically move or release pressure upon the work piece when fluid actuating pressure is reduced or lost. Furthermore, the machining tolerances must be accurately controlled among the majority of internal clamp component parts in order to achieve the desired component part motions and to achieve satisfactory clamping forces.
In accordance with the present invention, the preferred embodiment of the apparatus performs as a clamp with moveable members which generate a toggle action, or performs as a gauging device having a pair of moveable members which mechanically abut against each other to maintain, at least temporarily, a locking position of an arm even when actuating fluid pressures have been decreased or lost. In another aspect of the present invention, a lost linear motion device is provided in order to maximize arm unlocking forces. A uniquely configured slide, crank and hub are provided in a further aspect of the present invention. Methods of operating and assembling the present invention apparatus are also provided.
The powered clamp and gauging apparatus of the present invention is highly advantageous over conventional clamps since the present invention has a tapered self-locking feature for holding a rotated arm even after loss of piston actuating pressures. Thus, work pieces will not fall from their locked and/or gauged positions, thereby preventing work piece and equipment damage. Another advantage of the present invention apparatus is that slotted coupling between moving members allow for a toggle action which magnifies clamping forces without adversely affecting apparatus accuracy for gauging. The present invention is further advantageous by employing the specifically configured slide and crank in combination with a lost motion device in order to maximize unlocking forces while reducing the need for accurate component part machining tolerances. These more relaxed machining and part tolerances provide for lower cost manufacturing and reduced part scrappage while improving clamping and gauging force efficiencies and performance. The present invention apparatus is fully sealed and permanently lubricated and is therefore suitable for use in even the most contaminated environments. This powered clamp and gauging apparatus is also very compact and lightweight, and can have its clamping or gauging arm easily preset to any one of a number of positions. Additional advantages and features of the present invention will become apparent from the following description and dependent claims, taken in conjunction with the accompanying drawings.